Conveyor belts are supported and driven by a number of different idler rollers and pulleys, respectively. Among the many different idler rollers well known in the prior art are impact idlers, scale idlers, offset center roll troughing idlers, extended center roll troughing idlers, and return idlers. In general, the idler rollers may be either straight, or segmented and tilted so as to trough the conveyor belt and increase its volume capacity. Idler rollers are used both on the upper, load-carrying portion and the lower, return portion of the conveyor.
When ballast or other particulate material is deposited on the load carrying portion of the belt, the conveyor belt is supported from underneath by troughing rollers which trough the belt to increase the belt's volume capacity for particulate material. The troughing rollers come into contact with the clean side or inside of the load carrying portion of the conveyor belt.
After the load is discharged, sediment and debris from the load remain on the return portion of the conveyor belt. The return portion of the belt is supported from underneath by straight return idler rollers which, unlike troughing rollers, come into contact with the dirty side or outside of the return portion of the conveyor belt. The dirt and debris remaining on the outside of the belt after discharge is extremely abrasive and significantly reduces the wear life of the return idler rollers.
To prolong the wear life of the return idler rollers, it is known to provide circular, flat discs fitted on the rollers to increase their life. The circular, flat discs may be made of several different materials such as polyurethane, rubber ceramic or steel, for example, and are formed in various dimensions. The discs are provided with a central bore slightly smaller than the outer roller diameter. The discs are force fitted over the roller and held in place by the resultant frictional force.
While roller discs of this type extended the life of the roller assembly, these discs are very time-consuming to install and replace. To replace worn roller discs of this type, it is necessary to dismantle the roller assembly from its journal mountings. This task is burdensome due to the weight of the rollers and conveyor belt, and costly due to the resultant down-time of the conveyor. Another type of assembly provided in the prior art to extend the life of idler rollers comprises two longitudinally-extending, mating sleeve halves adapted to be clamped on an idler roller. A roller sleeve of this type is disclosed, for example, in U.S. Pat. No. 3,657,779. Roller sleeves of this type are an improvement over replacement roller disks but are still difficult to install and replace in the field, especially when the roller sleeve is in contact with the conveyor belt. In this situation, two or more men are required simultaneously to lift the conveyor belt weighing, for example, 30 lbs/ft, off the roller and to replace the roller sleeve halves.
Another significant problem encountered using roller sleeves of this type is eccentric wear after installation. The material at the boundaries between mating sleeve halves has a tendency to bulge outwardly when the sleeve halves are compressed and clamped together. The sleeve assembly then retains an eccentric or elliptical shape which significantly reduces the sleeve assembly's wear life. The eccentric shape of the sleeve assembly also greatly increases vibrations in the conveyor belt assembly.
Split roller sleeves of this type have, however, a significant advantage over replacement roller discs. Split roller sleeves are easy to remove by simply removing the clamping mechanism and allowing the two sleeve halves to fall off the roller. The two piece design of split roller sleeves similarly makes them easier to install than roller discs by eliminating the need to remove the roller from its journal mountings.
Idler roller sleeves may be made of several materials such as urethane, ceramic, and steel, and have a wear life of approximately two weeks to three months, depending on the environment in which they are used. In the most abrasive environments such as steel mills, even idler roller sleeves made from steel last approximately 2-3 weeks and require two men approximately four hours to replace when worn. It is therefore an object of the present invention to provide a roller sleeve which is easy and quick to install and replace under all conditions without disassembling the roller from its journal mountings.
It is also an object of the present invention to provide a roller sleeve which wears concentrically after installation which extends the wear life of the roller sleeve.